The present invention relates to a method, apparatus and composition for treating subterranean well formations, and more specifically, to an improved method and apparatus for treating a productive zone while drilling.
Hydrocarbon producing wells are often completed in unconsolidated formations containing loose and incompetent particulate solids which migrate with hydrocarbons or hydrocarbons and water produced by the wells. The presence of the particulate solids in the produced fluids is highly undesirable in that the solid particles abrade tubular goods, pumping equipment, valves and other producing equipment and reduce the fluid production capabilities of the producing zones in the wells. Incompetent subterranean formations include those which contain loose particulate solids that are readily entrained by produced fluids and those wherein the particulate solids making up the formations are bonded together with insufficient strength to withstand the forces produced by the production of fluids from the formations. A technique which is often used for minimizing particulate solid production from unconsolidated formations has been to produce fluids from the formations at low flow rates whereby the near well stabilities of particulate solid bridges and the like in the formations are preserved. However, the collapse of such particulate solid bridges often occurs as a result of unintentional high production rates and/or pressure cycling. Pressure cycling occurs from frequent shut-ins and start-ups of a well. The frequency of the pressure cycling is very critical to the longevity of the near well formation, especially during the depletion stage of the well when the pore pressure of the formation has already been significantly reduced.
To alleviate this problem, a number of solutions have been proposed. One such solution involves gravel packing the annulus between the well bore wall and sand control screens and the like, with sized sand or gravel to ensure that formation particulate solids are not produced during production of hydrocarbons. However, because gravel packs and sand screens filter out particulate solids from the produced fluids, the presence of the filtered particulate solids adds to the flow resistance thereby producing additional pressure draw down which causes portions of the unconsolidated formations to break down.
Another solution involves treating the subterranean formation with a consolidation agent, which functions to solidify the subterranean formation thereby improving its structural integrity. More specifically, the treatment method involves introducing the consolidation agent into the pore spaces of the formation in the vicinity of the well bore. Before the consolidating agent becomes hardened or cured, the excess consolidating agent in the pore space must be displaced by an overflush fluid to help retain the original permeability of the reservoir formations as high as possible.
There are a number of tools that have been proposed for introducing the consolidation agent into the pore spaces of the formation. Known tools generally comprise a pair of axially spaced packers, which define an annular space via which the treatment fluid is injected into the surrounding perforations. A limitation of such tools is that they are designed to inject a batch of treatment fluid over a limited length interval via perforations in the formation. If parts of the formation surrounding perforations at different levels in a well are to be treated, then the tool is moved to another level and the injection of a batch of treatment fluid is repeated once the tool has been positioned adjacent the perforations. In addition, to regain the permeability of the formations after the placement of the treatment fluid such as consolidating agent, a separate operation of overflush fluid placement must be followed to displace the consolidating agent occupying the pore space within the matrix of the formation before the material begins to cure.
At least one solution has been proposed to inject treatment fluids, such as sand consolidation agents, stimulation chemicals and/or overflush fluids over a long interval into a formation surrounding an underground well bore. The tool according to this invention comprises a tool body, which defines a longitudinal axis that extends in use in a longitudinal direction within an underground well bore; at least three axially spaced swab assemblies, which are carried by the tool body such that in use at least two axially spaced annular spaces are formed between the tool body and the well bore; and at least two treatment fluid supply conduits, which are each connectable in fluid communication with one of the annular spaces. This configuration forms at least two separate regions through which the consolidation fluid and other treatment fluids can be introduced into the formation. It thus enables the simultaneous injection of multiple treatment fluids into the formation, which in turn increases the efficiency with which the formation can be consolidated or otherwise treated. While it allows multiple treatment solutions to be injected into the formation over any length, it does so only after the well bore has been drilled, and therefore requires at least two sequential operations to drill the well bore and treat the formation.
Thus, there is a need for an improved method of completing wells in unconsolidated subterranean zones whereby the migration of formation fines and sand with produced fluids can be economically and permanently prevented while allowing the efficient production of hydrocarbons from the unconsolidated producing zone.